The color display ability of a liquid crystal panel is described by the number of bits of the gray scales that can be displayed on the liquid crystal panel over each kind of color channel. Currently, a 6-bit liquid crystal display panel is commonly used, the 6-bit panel referring to the panel that can display 2 to the sixth power, that is 64, levels of gray scales and have three color channels of red, green and blue (refer to as RGB thereafter for short), so that 262144 colors (64×64×64=262144) can be displayed. It can be deduced that a 8 bit panel displays 256 levels of gray scales and 16777216 (16.7M) colors can be displayed. It can be seen that the colors that can be physically displayed on the 6-bit panel does not reach 2% of that of the 8 bit panel yet. So color enhancement technique is employed for the purpose of shortening the difference between the 6-bit panel and the 8 bit panel and prolonging the lifetime of the 6-bit panel. The color enhancement technique mainly comprises a Pixel Dithering (refer to as PD thereafter for short) Algorithm and a Frame Rate Control (refer to as FRC thereafter for short) technique.
Discontinuous color scales 0, 4, 8, 12, 16, 20 . . . , 252 are provided by the 6-bit panel while continuous color scales 0, 1, 2, 3, 4 . . . , 255 are provided by the 8 bit panel, which result in the colors of the 6-bit panel less than those of the 8 bit panel. The principle of the PD algorithm is to switch adjacent colors locally in a short time to obtain the lacked colors using the visual retention effect of the human eye. The first method is to display the level 0 of the gray scale at the timing of T0, the level 4 of the gray scale at the timing of T1 repeatedly on the same pixel, to mix the two kinds of the pixel gray scale information by using the visual retention of the human eye, and thus 2 levels of the gray scale can be substantially obtained; the second method is to use a pixel square matrix formed of four pixels, in which two pixels on the diagonal direction display the same level 0 of the gray scale or level 4 of the gray scale respectively, and the color information of 2 levels of the gray scale can be obtained by users on observation distance. More color scales are obtained by the 6-bit panel by using this method.
FRC technique mainly utilizes the visual inertia of the human eye, which means that the feeling of human eyes to the brightness does not disappear immediately as the brightness of the object disappears, but disappears after a period of time. Take a simple case for example: firstly adjusting the screen of a CRT display to pure red color on full-screen, then switching to pure yellow color through one key on full-screen, at the instant of the switching, what we “see” on the screen is neither red nor yellow, but orange. The reason is that the previous red color has remained in the eye because of the visual inertia, and the newly incoming yellow color is superposed on the temporarily remained red color feeling, then we “see” orange, a color that does not exist originally. FRC technique utilizes this principium, and exhibits an all-color picture in an emulated manner by controlling the frame rate and the color between the adjacent frames properly and controlling the data output spatially and temporally, so that we “see” the color that cannot be displayed by the liquid crystal panel itself when the moving pictures are played on the liquid crystal panel.
Both of the PD algorithm and the FRC technique can enable the liquid crystal panel to obtain more color scales, and extend the number of colors that can be displayed to 16.2 M. Currently, there further is a Hi-FRC (High FRC) technique which can extend the number of colors to 16.7 M.
All of the above utilize the characteristic of the visual retention and the visual inertia of the human eyes, and realize the extension to the number of the output gray scales by controlling the output data of the pictures for a plurality of continues frames. The disadvantage is that flickering of the picture may occur when displaying some specific pictures due to the specific algorithm applied to the processing of the data; a grid strip may further occur visually for the gray scale picture that has been performed FRC operation, because the human eye can capture slight variation of the picture.